The present invention relates generally to skylights employing chromogenic filters, and more particularly, to improvements in the light harvesting, light control, electrical operation, electrical control and serviceability of such skylights.
Skylights are frequently employed in various types of structures for practical, as well as aesthetic reasons. They bring in natural light, reducing the need for artificial light. This saves electricity and reduces cost.
Various characteristics of the conventional tubular skylight can affect the wave length of the light transmitted. For example, as shown in FIG. 1, a tubular skylight A, as known in the art, may reduce UV transmission without significant reduction of visible light if light entering the tubular skylight reflects from a highly reflective, but UV absorbtive, tubular inside surface B. UV transmission may further be diminished by light passing through a collection dome C and a light diffuser D.
Finally, skylights have recently seen the suggested addition of chromogenic filters. Such filters hold the promise of controlling the intensity of light transmitted through a skylight. Various technologies for producing user-controllable chromogenic filters have been proposed. Examples include electrochromic filters, liquid-crystal filters, user-controlled-photochromic filters, polymer-dispersed-liquid-crystal filters, and suspended-particle filters. These are described in U.S. provisional patent application Ser. No. 60/091,678, filed Jul. 2, 1998 and U.S. patent application Ser. No. 09/347,807, Busbars for Electrically Powered Cells, now U.S. Pat. No. 6,317,248, and filed Jul. 2, 1999, and U.S. patent application Ser. No. 08/914,876, Chromogenic Window Assembly Construction and Other Chromogenic Devices, now U.S. Pat. No. 6,039,390, filed Aug. 20, 1997, each incorporated herein by reference.
The term user controllable is used herein in the same sense as in the above-mentioned U.S. Pat. No. 6,039,390, entitled Chromogenic Window Assembly Construction and Other Chromogenic Devices. There it is said:
The term xe2x80x9cuser-controllablexe2x80x9d is used in the sense that the appearance of a chromogenic device can be regulated. Photochromic devices, because their coloration is a function of light intensity, are not directly xe2x80x9cuser-controllablexe2x80x9d. However, systems incorporating photochromic devices can be designed in which users can regulate such devices. For the purposes of this application, those systems would also be considered xe2x80x9cuser-controllablexe2x80x9d.
Chromogenic light filters are very useful in regulating the light through skylights at the discretion of the user. A description of various user controllable chromogenic technologies is given in the U.S. application Ser. No. 09/347,807 filed Jul. 2, 1999, incorporated herein by reference. Typically, such chromogenic devices are based on electrochromic technology, user controllable photochromic technology, liquid crystal technology and suspended particles which orient in an electric field. User controlled thermochromic devices (U.S. Pat. No. 5,525,430, incorporated by reference herein) have also been suggested where the user can vary the temperature of the chromogenic member to alter its transmission. Chromogenic filters are useful for both tubular skylights and conventional skylights. One example of technology useful for chromogenic filters is the electrochromic device discussed by N. R. Lynam and A. Agrawal in xe2x80x9cAutomotive Applications of Chromogenic Materials,xe2x80x9d Large Area Chromogenics: Materials and Devices for Transmittance Control, C. M. Lampert and C. G. Granqvist, editors, Optical Engineering Press, Bellingham, Washington (1989), which is hereby incorporated by reference.
The present invention relates to improving:
(1) Effectiveness of light harvesting by a skylight and reduction of sharp images or light patterns in the building interior such as might adversely affect a work area.
(2) Placement of sensors in the skylight system to effectively control the transmittance of the light through the chromogenic filters.
(3) Skylights with mechanical shades.
(4) Skylights in which the power to the chromogenic filters is provided by solar cells and that preferably are remotely activated by the user so that they can be easily retrofitted.
(5) Serviceable chromogenic light filters that can be easily repaired and/or replaced.
In accordance with the present invention, user-controllable chromogenic skylights are provided with improved light control. In a preferred embodiment, the invention provides for user control of the intensity of light from a skylight through the control of a chromogenic filter in combination with one or more of a remotely controllable mechanical shutter that provides darkness during the day and an internally mounted lamp to provide nighttime illumination. Short of complete blockage of light by the mechanical shutter, intermediate light intensity control is achieved by control of the user-controllable chromogenic filter.
All type of skylights will benefit from this invention, but some aspects of this invention are more suitable for the tubular skylights.
Like skylights described in the above-mentioned patent applications, skylights embodying features of the current invention may have an outward end with a light capturing dome, a tubular light path and an interior diffuser capping the skylight""s inward end. In this configuration, the chromogenic filter resides within or at the end of the tubular light path below the exterior dome. As the light travels through the skylight, its intensity is modified by the chromogenic filter that intercepts the light path. The skylight optionally includes a secondary diffuser (or diffusers), the mechanical shutter and the lamp. Control circuitry is provided for the chromogenic filter, the lamp and the mechanical shutter. Preferably, the control circuitry for the chromogenic filter, the shutter and the lamp share a single user-accessible interface by which the user sets the chromogenic filter transmittance, opens or closes the mechanical shutter, turns the lamp on or off, and perhaps sets the lamp intensity.
A user interface can be hard-wired into the control circuitry. Preferably, it is linked by radio frequency or infrared transmission. A sensor to receive an infrared transmission is located to be in a direct line of sight of the user interface. In a preferred embodiment, it is located out of sight behind the interior light diffuser. Also, in a preferred embodiment, multiple sensors increase the area within the building interior from which line of sight communication by a user""s remote control interface is available. Preferably, a visible or audible indicator communicates that the sensor has received the user""s commands. The indicator can be a simple lighted or flashing LED, an audible tone generator, a bank of LEDs connected to act as a bar graph, an alphanumeric display, etc. The indicator is particularly useful to signal the receipt of a command and the start of a change of transmittance by the chromogenic light filter since this is a gradual change not immediately apparent.
The chromogenic filter allows for user control of the intensity of light and possibly color that is transmitted through the skylight. Any of a number of chromogenic materials can function in this invention as mentioned above. Chromogenic materials change transmittance in response to an external signal. For example, electrochromic materials change transmittance based on an applied electrical potential. A filter control circuit supplies the electrical potential (the filter signal), which causes a transmittance that corresponds to a light intensity set-point. The light intensity set-point of the filter control circuit is substantially under the user""s control.
In one embodiment, the chromogenic filter closes the interior end of the skylight rather than the diffuser. A diffuser is located intermediate the light harvesting dome and the filter. This filter can be frosted or patterned such as with hemispherical or pyramidical crests or valleys. This arrangement makes the change between bleached and colored phases of the filter very apparent to building""s occupants and increases the visual attractiveness, which is to say the aesthetics, of the product. Further, since the light travels through two independent panes (the outer dome and the diffuser) before reaching the chromogenic filter, the opportunity for the UV rejection is high. One or both of these can be made out of plastics which block the UV light, one of these may block out lower wavelengths of UV (typically the outer dome) and the other one the longer wavelengths in UV, or both may even be similar, and this will result in a higher UV attenuation. The second filter should preferably be located close (within 12 inches) to the chromogenic filter and may be flat or curved. In a preferred embodiment this filter has one or more of the following characteristics:
Is curved like a part of the sphere, with the concave side facing the chromogenic filter,
Is patterned,
Is made out of plastic, preferably acrylic or polyearbonate, and
Has its edges close to (within 6 inches) or touching the chromogenic filter.
Automatic adjustment of the transmitted light occurs when the filter control circuit (the controller) includes a light sensor that responds to fluctuations in ambient light and adjusts the filter""s transmittance accordingly. The light sensing ability of the filter control circuit is provided through a light sensor that generates a signal related to the amount of light incident on it. Once a set-point is chosen, the filter control circuit adjusts filter transmittance by modifying the filter signal so that the signal from the light sensor remains at the value set by the user. Preferably such a sensor should be located below the chromogenic filter. This way the sensor can provide feedback to the controller on the intensity of the light passing through the filter. The filter control circuit can optionally institute filter maintenance procedures such as purposefully bleaching or cycling the filter during periods of non-use to maintain the filter""s performance. This maintenance may also be done by the controller itself after the filter has been activated for a pre-set period. The automatically adjusted chromogenic filter can readily be integrated into a HVAC system for a building.
Used in association with a chromogenic filter, the mechanical shutter provides coarse control over the intensity of the emitted light. Alternatively, the mechanical shutter can provide a means of light intensity control and the chromogenic filter the means for color control. When closed, the shutter blocks substantially all incoming light. When open, the shutter allows substantially all incoming light to pass. Used as the sole light intensity modifying element, the shutter can provide complete control of light transmission through the skylight providing varying degrees of brightness from complete blockage of light to full brightness. The shutter is preferably coated with diffusive or reflective material or possesses such a surface. It can also serve as a base for solar cells as discussed below.
The internal lamp allows the skylight to provide illumination after dark. If the lamp is positioned below the mechanical shutter, a reflective coating or finish of the closed shutter causes lamp light traveling away from a building""s interior to be reflected back towards the interior. The lamp control can have simple on/off control or can incorporate a dimmer. Under control of the intensity sensor of an automatic control circuit, the lamp can supplement transmitted light on overcast days.
Control of the light improves its quality and suitability for diverse interior activities requiring different lighting conditions. The increased control helps prevent undesired brightness or darkness inside the building.
The chromogenic filter generally is constructed of one or two, substantially transparent, rigid substrates. For single substrate construction, multiple coating layers are used, whereas in two-substrate constructions, fewer coatings may be used. The two-substrate constructions are sealed around the edge, and define an enclosure for and electrical contact with the chromogenic material. Electrical contact is provided through a conductive film bonded to surfaces of the substrate.
Certain embodiments of skylights constructed in accordance with the invention provide for softening or reducing transmitted light by modifying or adding components to the skylight to increase diffuseness of the light. It can be accomplished using diffusers, by applying diffusive coatings to the chromogenic filter, or by increasing the light-scattering ability of the chromogenic filter itself. Coating the interior surfaces of the skylight with diffusive paint or other diffusive material increases the diffuseness of the light. Alternatively or in connection with that, diffusers, i.e. translucent lenses, are used to increase the diffuseness of the light. Furthermore, in some embodiments of the invention, the chromogenic filter supplements or may provide substantially all of the skylight""s light-diffusing ability.
To alter the diffuseness of the filter, the filter can be coated or laminated with a diffusive material coating or layer, or the chromogenic material can be modified to be more diffusive. For the purpose of coating or laminating, suitable coating materials include polyester, alkyds, polyurethanes, acrylics, epoxies, silicones applied, for example, to the outside surface of the filter with one or more of silicates, silica, titania, zinc oxide, clays and ceramics dispersed therein. Modification of the chromogenic material for diffuseness primarily consists of mixing a diffusion imparting material into the chromogenic material. The filters may also be coated with thenmochromic materials, which become more opaque or acquire a color as their temperature rises.
In one preferred embodiment, the outer dome is comprised of a first material which carries dispersed particles of a second material. As temperature varies, the refractive index of one or both materials changes so that the light transmissive qualities of the layer varies. These materials are thermochromic where their light transmission property changes with temperature. The dome may also be made out of the photochromic material. Another light modifying addition to one or more elements of the skylight that transmit light is antireflective coatings to increase the transmission of light incident on the element so-coated.
Thermochromic or a photochromic material coating can be applied to the outer surface of one of the chromogenic filter substrate or one of these substrates may themselves be made out of one of these materials. All of these schemes allow the outer dome to have thermochromic and/or photochromic properties which can be used in conjunction with the chromogenic filters.
To provide a skylight that minimizes UV light transmission while not unduly lowering visible light transmission, UV absorbers that do not significantly absorb visible light can coat the filter, can be mixed with the chromogenic filter, or can be added to the light diffusers or the dome. Types of UV absorbers or filters that can be used are clear plastics that cut off or absorb strongly in the UV region of the solar spectrum which is from about 290 nm to 400 nm. The cutoff wavelength of the filter should be in the range of 380 to 400 nm. This means that the transmission of the filter is 30% or lower at this wavelength and continues to decrease below this wavelength, so that it transmits less than 5% (preferably less than 1%) 20 nm below the cutoff point. The filter should keep its absorption below 1% to at least down to 290 nm, preferably down to 250 nm. An example of the preferred filter is. Examples of such plastic filters are Acrylite OP-3 from Cyro Industries (Rockaway, N.J.) in a thickness range of 0.125 inch, UV filter film (catalogue number 394267) from Edmund Scientific (Barrington, N.J.), Flexmark OA 200 UV, V22 (from Flexcon, Spencor, Mass.), CLS-200-XSR from Madico (Tempe, Ariz.). Further, these filters may be embossedxe2x96xa1m with light diffusing patterns and or have infrared blocking properties. Counting the outer dome the above describes up to two UV filters or light transmission panes are placed between the chromogenic filter and the outside environment, however, one may place more filter elements to provide higher UV rejection, patterns, colors, etc.
In one preferred embodiment, solar cells partially or fully provide the electrical requirements of the skylight. The solar cells can be roof mounted, mounted on the outward portion of the skylight (not blocking the light dome), or mounted in the interior of the skylight (meaning inside of the outer dome).
For convenience in repair, cleaning and filter replacement, an innermost diffuser capping the interior of a light tube is readily removable to allow access to the filter, which is also removably mounted and has electrical jacks or connectors easily disconnected. The chromogenic filter is located within reach of the interior end of the skylight and any electrical connections are designed for quick and convenient disconnection and reconnection. The control circuit is housed in a housing affixed to the light tube and is accessible through a hinged door that is formed as a part of the light tube interior surface. The door preferably has the same reflective or diffusive surface qualities as the interior surfaces of the tube. In a conventional skylight such controller boxes can be accommodated within the skylight frame or are mounted between the dome and the chromogenic filter or mounted outside the skylight which may be weather protected.